THE MICROSCOPE

Evening Star, Issue 19298, 10 July 1926, Page 18

THE MICROSCOPE

SOME OF ITS WONDERS BEAUTIFUL LIVING BELLS No. 111. [Written by G. A. Rawson, for the 1 Evening Star,’] I have before me, as I write, a glass jar filled with duckweed and other aquatic plants gathered from an ordinary fresh-water pond. With a pair of delicate forceps I detach a few feathery branchlets from the stem of one of these plants, and place them in a narrow glass tube, which I fill with some of their native swamp water. Now lot us take a fairly powerful pocket magnifying lens, and, holding the tube against a good light, examine its contents carefully. Soon we see, dotted about at irregular intervals over the little branches and leaves, what appear to bo thin patches of white fluff. Watching one of these patches closely for a few moisonts, we notice that a movement is taking place in it, and that certain parts seem to be alternately contracting and expanding. We will now transfer a small portion of the weed, together with its fluffy material, to a glass slip; add a little water, cover over with a cover glass, and place on the stage of the 'microscope. Employing a low magnification at first —say, fifty diameters what do wo see? Well, we see that we have secured a colony of some of the commonest, as well as some of the most beautiful, of the innumerable denizens of our ponds—namely, the well-known 8011-animalcules, or Vorticella. they are lowly ■unicellular creatures belonging to the great class of the Protozoa. What exquisitely lovely objects they are, as they disport themselves under our microscope 1 Clear and transparent as the most flawless crystal, see how they are in almost perpetual motion 1 Each little body is shaped like an elegant antique urn, or cup, or hell, and is situated on the end of a long stalk, as (feheuto rus ft gossamer thread, aiui about six times as long ns the little urn. These stalks are seen to spring fr« i;ii the midst of the flocculent matter ;r' iclied to the plant, and ns they . end they diverge, so as to carry thenlovely little bells clear of one another. This stalk is capable of contracting spirally when the creature is disturbed, and coils up liko a corkscrew, after the manner of a spiral spring. This movement is effected by a peculiar fibre, which passes down the inside of the stalk throughout its entire length,_ and in the larger species is distinctly visible as a narrow dark band. Although we cannot recognise in its structure some of those characteristic features which distinguish the muscular tissues of higher animals, yef wo are forced to conclude that this spiral ribbon is a rudimentary form of muscle. The appearance of such a group of Vorticella reminds one strongly of a beautiful bunch of tiny lillies. But they far surpass in loveliness any flower that ever bloomed. Look! One has disappeared with a sudden movement. Has it dissolved away? No; it has only drawn back, with a rapidity which the eye cannot follow. There is its urn-shaped body, withdrawn almost to the very base of its stalk. Elero it comes again, moving slowly forward, with its stalk coiled liko a spring whoso spirals gradi ally straighten out as the stem lengthens; until at la it is stretched out tight and all 1.. j curves disappear. This is about as much as a low-power microscope will reveal to us, for the body of tho creature measures hardly more than one-thousandth of an inch across; so we will now substitute a fin objective for the one wo have been employing. With this greatly increased magnification we soon see that tho bell or cup is not such a simple structure as we were inclined to imagine at first. We were able to see that it was fixed at its base to the top of tho stalk; now we observe that its upper end thickens so as to form a mi, which is called the peristome. Inside the peristome is what is known as the disc, which is more elevated on one side than on the other. A depression between the rim and the raised side of the disc forms tho mouth, which opens into a conical gullet. By carefully adjusting the focus we see that the inner border of the peristome, or gullet, and the disc are encircled by a wreath of cilia, or fine lashes, which are in rapid vibration, and by their successive contraction in tho_ same direction they produce the optical illusion of a toothed wheel revolving. Watching the cilis closely we notice the vortex created by their movements, which causes all the little particles floating in tho vicinity to dance in a lively whirlpool motion around every momentarily stationaiy vase. Every now and then some of these particles, suitable for food, are drawn into the month and so pass down tho gullet. But although tho Vorticella have a mouth and a gullet, yet they have no stomach wherein to bestow the food they have captured. What, then, becomes of it? It is simply absorbed into the protoplasm of the body-mass. As each particle becomes ingested it is surrounded bv a tiny globule of water, tho whole forming a littio sphere called a food vacuole. These circulate in the inner protoplasm until they aro absorbed. Particles which cannot bo digested aro ejected at the base of the gullet, and returning currents carry them out of the mouth. It is easy to feed these tiny creatures, and then watch the whole process of absorption under the miscroscope. According to Professor Sir E. Ray Lankester. boiled bacteria mako a highly suitable food for them.

Before introducing some boiled bacteria into tho water in which the Beilnniraalcules aro displaying their charms under our microscope, it will be as well to stain them with an alkaline blue, such as blue litmus. They are soon observed to be whirling about in the ciliary vortices, being gradually driven into the mouth cavities. As they pass into the animals’ bodies their blue color is seen to change to red, indicating that an acid has been secreted by the protoplasm in the little globule of water winch surrounds them. “In the course of a few minutes,” says Ray Lankester, “ yon will see the little sphere of water dwindling in size—the nourishing liquid being absorbed by the protoplasm—and then you will see the undigested fragments passed on by a slow movement to the vestibule or pit of tho mouth, extruded through a temporary opening through the protoplasm, and whirled away by the water currents.”

Reproduction takes place by fission—that is, by one individual dividing into two, as is the case with all the Protozoa. But, as I have pointed out on former occasions, this process cannot go on indefinitely, and _ at intervals there has to be a “ conjugation.” or fusion of two distinct individuals, resulting in a rejuvenescence, or renewal of the capacity to multiply. In the colony of Vorticella, under our observation, wo see some of the stalks bearing two vases, instead of one. The process of reproduction is taking place liere, and these two are the result of the spontaneous splitting of one. In other specimens we may observe the process in different stages. For instance, here is one individual which, instead of being vase-shaped, has become globular. Very soon we notice a depression forming in tho middle of its front outline, which deepens until it becomes & deft. M this enlarges

and tliQ division continues down- j wards, the ruptured edges of the two j halves heal simultaneously, so that , they remain perfectly smooth and j rounded. At length we have two perfect vases side by side on the same stem, where before there had only boon one. One of these is ultimately thrown off while the other remains on the stalk. The cast-off one, after roving about as a free-swimming organism for a W'hile, will then settle down and affix itself to a suitable spot by the point which -.was formerly its mouth. A now stalk will gradually grow, and a new mouth will open > in the midst of the new crown of cilia which will quickly develop. To watch a colony of Vorticella under the microscope is indeed a beautiful sight, as they dart in and out on their stems, and sway gracefully to and from in the water, with all their cilia in rapid motion. As that charming writer and unrivalled observer of Nature’s hidden beauties, the late P. H. Gosse, F.R.S., has well said: “ It is not until we view these creatures with a good microscope that we acquire an adequate idea of their beauty. Of their brilliant transparency, their sudden and sprightly motions, their general elegance and delicacy, and the apparent intelligence with which they are endowed, neither books nor engravings had given mo any conception, nor, indeed, can they!”